1. Field of Invention
This invention relates to the creation of a class of materials that do not exist in nature through grafting on man-made polymers onto protein backbone that combine the characteristics of both proteins and polymers. Proteins usually provide adhesion and the polymers the three dimensional crosslinking.
2. Description of the Prior Art
In the second half of the 20th Century, man-made polymers have become indispensable for daily life. From clothing to construction materials to binding metals together, they provide useful and sometimes indispendsable materials. However, they generally represent the end products of the petroleum industry, and in addition to being dependent on the fluctuations of that industry, they come from a source that is bound to run out. Proteins, on the other hand, have traditionally been considered primarily as food, and certain proteins such as collagen and casein were used as structural or paper adhesives. They have never been considered suitable as a source of high performance materials, even though, in the dry state, collagen has 10,000 p.s.i. tensile and over 3,000 p.s.i shear strength. This was basically due to moisture sensitivity of most proteins which resulted in protein bonds losing their mechanical properties and being attacked by microorganism. Compared with epoxide or phenolic resins, which have remarkable mechanical strength as well as moisture resistance, this shortcoming of proteins can be raced to the absence of three dimensional crosslinking. Certain proteins, on the other hand, such as barnacle cement and mussel adhesive, have the ability not only to set in the presence of water but also to be unaffected by it as well as by proteolytic enzymes. Barnacle cement can even bind to "Teflon". Available evidence shows clearly this resistance to be due to very tight three-dimensional crosslinking. It is easy to conclude, then, that if proteins could be modified appropriately so that they could be crosslinked with sufficient density, they, too, would be resistant to moisture as well as proteolytic degradation. They could then function as building blocks to high performance adhesives, coatings and structural materials.
There have been several attempts to graft acrylics, vinyls, etc. onto leather to improve its qualities, mostly moisture resistance and epoxides to develop new tanning methods but no attemps were made to specifically modify the backbone of a soluble protein to produce a new material.
Furthermore, in contradistinction to pertoleum based polymers, proteins represent a renewable resource.